The present invention relates to nuclear magnetic resonance (NMR) spectroscopy and, more particularly, to a novel method for polarization transfer by a selective homonuclear technique (POTSHOT) for suppressing response signals from at least one selected resonance of uncoupled spins while retaining response signals from at least one other selected resonance of coupled spins. In typical use, all uncoupled spin respohse signals are suppressed, as are all coupled spin response signals except those from a preselected spin system.
It is now well known that nuclear magnetic resonance (NMR) in-vivo phosphorous (.sup.31 P) spectroscopy is a useful tool for monitoring human metabolism. However, in-vivo phosphorous spectroscopy suffers from the relatively long time interval (typically at least ten minutes) required for acquisition of a spectrum with reasonable signal-to-noise ratio. The length-of-time problem might be avoided if hydrogen (.sup.1 H) spectroscopy could be utilized, instead of phosphorous spectroscopy, because the NMR sensitivity of hydrogen is roughly fifteen times as great as the phosphorous sensitivity; hydrogen spectroscopy has a data-collection time which may be two, or more, orders of magnitude less than the data-collection time for phosphorous, if the same signal-to-noise ratio is to be achieved. However, it is well known that .sup.1 H spectroscopy suffers from the presence of uncoupled-spin resonances from certain components, such as water and the like, and from the presence of coupled-spin resonances, such as lipids and the like, of the sample to be investigated, which are typically four orders of magnitude and three orders of magnitude, respectively, larger than the spectral peaks of interest (e.g. lactate components and the like). Further, these undesired uncoupled-spin resonances are positioned approximately at the same spectral position as the desired metabolite peaks, rendering the detection of the desired metabolite peaks virtually impossible by conventional techniques. Accordingly, it is highly advantageous to provide a method for acquiring spin resonance responses from coupled hydrogen spins in metabolites in in-vivo human samples, in the presence of in-vivo human tissue components, including water, lipid and the like substances, having uncoupled hydrogen spin resonances.